The Technology Vent and Rant Thread

[JSWolf]

Originally Posted by Quoth

CD to CD is only 1:1 for CD-ROM, not CD-Audio as audio has no error correction, though mostly the results are better than analogue tape and very many more generations are possible.

I used to have a DVD drive that allowed me to make a 1:1 copy of an audio CD in some cases. It was not 100%.

[ratinox]

Originally Posted by JSWolf

I used to have a DVD drive that allowed me to make a 1:1 copy of an audio CD in some cases. It was not 100%.

Next time use EAC or CUERipper and use the AccurateRip database to ensure bit perfect copies.

[Quoth]

Originally Posted by ratinox

Next time use EAC or CUERipper and use the AccurateRip database to ensure bit perfect copies.

But Audio CDs don't have error correction. They replace errors with silence.

Several different copies of the same Audio CD will not be identical (pressed or written). See the Red Book.

[JSWolf]

Originally Posted by Quoth

But Audio CDs don't have error correction. They replace errors with silence.

Several different copies of the same Audio CD will not be identical (pressed or written). See the Red Book.

The CD player will try to correct the error. In most cases, it works so you don't notice the error.

[ratinox]

Originally Posted by Quoth

But Audio CDs don't have error correction. They replace errors with silence.

Several different copies of the same Audio CD will not be identical (pressed or written). See the Red Book.

Neither of these assertions are correct.

Audio CDs use cross-interleaved Reed-Solomon (CIRS) error correction. They only replace errors with silence (or pops on bad kit) when errors exceed the drive's error correction capabilities.

It is entirely possible to achieve bit-perfect audio CD rips and verify that they are exactly the same as other rips, and to correct ripping errors. This is precisely what the AccurateRip database is: a database of drives, offsets, checksums, etc., to guarantee accurate, bit-perfect rips.

I have approximately 500 CDs in my library verified through the AccurateRip database. I know they are exact, bit-perfect rips because the checksums match the checksums in the database.

http://dbpoweramp.com/spoons-audio-guide-cd-ripping.htm

[j.p.s]

Originally Posted by ratinox

Not exactly. CD-DA (Digital Audio) does have error correction but it's only two rounds of Reed-Solomon coding which is sufficient for single bit errors. Full error correction requires three rounds of RS coding. CD-ROM uses three rounds.

Originally Posted by ratinox

Neither of these assertions are correct.

Audio CDs use cross-interleaved Reed-Solomon (CIRS) error correction. They only replace errors with silence (or pops on bad kit) when errors exceed the drive's error correction capabilities.

According to wikipedia, CIRC as implemented on CD corrects burst errors of up to 4000 bits. (The spatial interleaving avoids the need for an impossible number of parity bits. The
wikipedia article is very weak on detail.)

[Quoth]

See
https://audio-union.com/audiophile-i...-of-audio-cds/

It's possible to have CD Audio and CD-ROM with same amount of "damage" and the data CD can have an exact copy, but Audio CD won't.

Also "written" rather than pressed CDs can deteriorate faster, that's why there was/is archival quality versions.

I have many 30 year old approx "written" CD Audio, CD-Data and Bureau Photo CD discs. Some of the Audio CDs are now audibly "damaged". The CD-data and photo CD are all fine.

1:1 copies are not assured with CD-Audio, but it's a lot better than CD Audio > minidisc > CD Audio. Only wav or similar files on CD-ROM are better.

You might often get 1:1 with CD Audio. The fact you always have doesn't mean it's always true.

[ratinox]

Originally Posted by Quoth

See
https://audio-union.com/audiophile-i...-of-audio-cds/

It's possible to have CD Audio and CD-ROM with same amount of "damage" and the data CD can have an exact copy, but Audio CD won't.

Yes, because audio CDs have less error correction than CD-ROM. Not no error correction.

Also "written" rather than pressed CDs can deteriorate faster, that's why there was/is archival quality versions.

I have many 30 year old approx "written" CD Audio, CD-Data and Bureau Photo CD discs. Some of the Audio CDs are now audibly "damaged". The CD-data and photo CD are all fine.

Because consumer CD-R media uses an organic dye which will deteriorate when exposed to oxygen. Your data discs are not "fine"; they're just working longer because CD-R has more robust error correction than CD-DA. I'm afraid your burned audio discs likely are unrecoverable if you don't have the original, commercially pressed discs around.

1:1 copies are not assured with CD-Audio, but it's a lot better than CD Audio > minidisc > CD Audio. Only wav or similar files on CD-ROM are better.

You might often get 1:1 with CD Audio. The fact you always have doesn't mean it's always true.

It's true that any single user with a single drive is likely going to have problems getting perfect rips every time. Get a large enough collection of people, drives, and duplicate discs together and you absolutely can get consistent, perfect rips. That's what the AccurateRip database is: 500K users, 5000 unique drives, and 5 million unique discs cataloged.

Originally Posted by j.p.s

According to wikipedia, CIRC as implemented on CD corrects burst errors of up to 4000 bits. (The spatial interleaving avoids the need for an impossible number of parity bits. The wikipedia article is very weak on detail.)

I had forgotten just how wide CIRC on CD-DA would work. I did remember that single bit errors were easily corrected, which got stuck in my head. It's still not as robust as the layers of error correction on CD-ROM.

[Quoth]

Originally Posted by ratinox

I'm afraid your burned audio discs likely are unrecoverable if you don't have the original, commercially pressed discs around.

I'd never duplicate a commercial CD to CD. Certainly Rip to my server, for my own playback on my phone. The only PC written CD Audio discs I had were for playing back live recordings in 1994-1997. Better than cassette and the CD player was almost portable (A Philips Photo CD CDF100 I still have). I never had the battery pack, though I suppose I could make one. It also plays Portfolio CDs (A format killed by Kodak's pricing) and a rep gave me a demo one.

There are tape cartridges. Dubious if they work or the PC Drive is available, or there is an interface for PCI (I have some computers with PCI) or PCIe.

CDs of live recording to HDD. Turns out that an old HDD in a drawer lasts better than non-pressed CDs. I actually also have the original wav files on the current server and its backups

Last year I managed to copy some CP/M files off 3.5" where the drive had been used in place of a 3" on a PCW8256.

I've only lost a couple of important files ever, and no important files since about 1989.

Can't have too many backups.

Because consumer CD-R media uses an organic dye which will deteriorate when exposed to oxygen.

Sunlight is also bad as a customer found out in the early 2000s. He'd left the CD on a window sill, label side down Maybe only a few weeks.

Even CD-Data is isn't a backup media. Perhaps MO disks are reliable. I've not used the computer kind since late 1990s and never had my own drive. My nearly 25 yo Minidiscs seem fine. As is the player which was lying in the corner of a friend's workbench unused for 19 years, so he gave it back to me a couple of months ago. Fortunately this works https://web.minidisc.wiki/
He also gave me back the heap of blank discs I'd given him (still wrapped) and the one I tested was OK.

Shame Sony crippled the format. I doubt files on an SD card keep as well. A relative's SSD went blank 2 weeks ago. She'd not done backups. Seemingly dead to all tools. Laptop now has a new SSD. Will she do backups?

[Quoth]

And I apologise for claiming CD-Audio has no error correction. It has some, and that's appropriate for pressed CDs and compromise between playing time and overhead. CD-Data is far better, but still not an archive medium on PC writing. Nor is DVD. We used DVD Video recording for a few years as better than VHS, but it was quickly eclipsed by other schemes. I also used Digital 8 for a while. The late 1990s Analogue 8mm Video tapes still work on the Sony Digital 8. I should transfer them to HDD before they fade. I got a low height PCIe Firewire card for my shoebox workstation and the camera plays back to HDD on Linux.

[ownedbycats]

Originally Posted by Quoth

I have many 30 year old approx "written" CD Audio, CD-Data and Bureau Photo CD discs. Some of the Audio CDs are now audibly "damaged". The CD-data and photo CD are all fine.

Originally Posted by ratinox

Because consumer CD-R media uses an organic dye which will deteriorate when exposed to oxygen. Your data discs are not "fine"; they're just working longer because CD-R has more robust error correction than CD-DA. I'm afraid your burned audio discs likely are unrecoverable if you don't have the original, commercially pressed discs around.

CD-Rs - I have a lot of old burned backup discs of different brands. They were stored in various ways (spindles, CD binders, loose in a plastic box...), age between 15-25 years old. I went through them a year or two ago. The one brand of disc that every disc was still perfectly readable was Verbatim.

I've also heard that JVC (Taiyo-Yudens) have similar reliability but I haven't any from then.


I remember plenty of coasters (failed burns) from cheaper budget brands. I put one in a microwave to see what would happen. Made the kitchen smell bad for a while (nice light show though).

[ratinox]

Originally Posted by Quoth

And I apologise for claiming CD-Audio has no error correction. It has some, and that's appropriate for pressed CDs and compromise between playing time and overhead.

CD-DA has a lot of odd compromises. Like how the recording time is 74 minutes, 33 seconds allegedly because that's the duration of a particular recording of Beethoven's Ninth Symphony.

CD-Data is far better, but still not an archive medium on PC writing. Nor is DVD.

Again, because the recording layer on CD-R and DVD-R is an organic material. Quickly degrades when exposed to oxygen.

Some brands are superior, as ownedbycats discovered. Verbatim and JVC/Taiyo-Yuden have the best reputations for both recording reliability (few/no coasters) and durability.

MO media should last forever barring physical damage. The metallic recording layer is inert, and it's non-magnetic except when under heated phase change conditions.

[Solitaire1]

Originally Posted by ratinox

CD-DA has a lot of odd compromises. Like how the recording time is 74 minutes, 33 seconds allegedly because that's the duration of a particular recording of Beethoven's Ninth Symphony.



Again, because the recording layer on CD-R and DVD-R is an organic material. Quickly degrades when exposed to oxygen.

Some brands are superior, as ownedbycats discovered. Verbatim and JVC/Taiyo-Yuden have the best reputations for both recording reliability (few/no coasters) and durability.

MO media should last forever barring physical damage. The metallic recording layer is inert, and it's non-magnetic except when under heated phase change conditions.

I know that a Red Book CD doesn't have a file structure because at the time it was created that wasn't a concept. A Red Book CD stores the audio as one continuous groove, similar to the way audio is stored on an LP/45/78. It also contains a Table of Contents (TOC) that tells it where each track is on the disc. This is why Red Book CDs are gapless, the audio itself doesn't have gaps (unless silence is put in the source audio).

In a way, it is similar to the Minidisc which contains a TOC to tell the player where the tracks are. That's why you can delete and reorder tracks on a Minidisc. The tracks are recorded in a manner like on a floppy disc and the TOC tells it where each track is. Reordering the tracks just involves rewriting the TOC. If you delete a track on a Minidisc the track is not actually deleted, instead the recorder just deletes the track and it's space from the TOC and that space is freed up for future use and it may eventually be overwritten. However, that's why it is critical to ensure that the TOC can be properly written, if it is not all of the tracks could be lost.

As far as the maximum playing time on a Red Book CD, if you push everything to the absolute limit of the Red Book Standard without violating it, it is possible to fit almost 80 minutes of audio on a CD. However, the Red Book Standard doesn't establish a maximum amount of audio on a CD, just the standards for the CD itself (thickness diameter of the disc, the tolerances for the data recorded to the disc, and so on). This is why DualDiscs ("CD" on one side, DVD on the other) cannot be legitimately called a CD because the disc is slightly thicker (IIRC it is 4 microns thicker than the standard CD).

Concerning the 74-minute limit for audio, I think it was established as safe standard to deal with the limitations of the technology. Later, as the technology was improved it was possible to fit more audio on the CD without violating the Red Book Standard.

Concerning CD-Rs themselves, I don't consider them a long-term storage option. Instead, I see them as almost disposable. If one fails, I just burn another one.